In laser amplifiers or oscillators, typically employed in a system for isotopically selective photoexcitation, and more particularly as may be shown in U.S. Pat. No. 3,944,947, it is desired to be able to provide pulsed lasing of a flowing dye solution with high pulse rate and high power operation. The transverse pumped dye laser has been recognized as providing a channel configuration conducive to high pulse rate and high energy lasing. This is particularly so because the transverse flow of laser material passing on axis of optical excitation insures that the excited and heated particles will be swept beyond the active lasing region in the most rapid manner thereby providing a fresh supply of laser material at high rate. Additionally, with transverse pumping, heat generated in the lasing process within the lasing medium is rapidly carried from the active lasing area so as to minimize heat induced refraction variations that degrade laser beam quality.
While providing the conditions for high pulse rate and high energy lasing, it is also essential for applications of laser enrichment that the beam of laser radiation generated or amplified by the dye laser be of very high quality, that is exhibit very low divergence. This is particularly true where the produced laser beam is to traverse long distances, comprising many meters, of path length through regions which produce isotopically selective photoexcitation in the enrichment process.
While the basic configuration of a transverse pumped dye laser is known, as for example shown in U.S. Pat. No. 3,740,665, the means for creating conditions in the flow of laser material which permit high pulse rate and high energy lasing with very high laser beam quality have been less clearly understood.